srtp_driver: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/lib/srtp/bin/srtp_driver - from package: srtp-utils

You may install the required package with command apt-get install {package}
Error in other languages:
srtp_driver: bevel nie gevind nie
srtp_driver: comandă negăsită
srtp_driver: comando não encontrado
srtp_driver: commande introuvable
srtp_driver: command not found
srtp_driver: käsku ei ole
srtp_driver: không tìm thấy lệnh
srtp_driver: komanda nerasta
srtp_driver: Kommando nicht gefunden.
srtp_driver: kommandot finns inte
srtp_driver: komut yok
srtp_driver: nie znaleziono polecenia
srtp_driver: níor aimsíodh an t-ordú
srtp_driver: no se encontró la orden
srtp_driver: no s'ha trobat l'ordre
srtp_driver: opdracht niet gevonden
srtp_driver: parancs nem található
srtp_driver: perintah tidak ditemukan
srtp_driver: príkaz nenájdený
srtp_driver: příkaz nenalezen
srtp_driver: команда не найдена
srtp_driver: командата не е открита
srtp_driver: 命令找不到
srtp_driver: コマンドが見つかりません